U.S. patent application number 12/050655 was filed with the patent office on 2008-07-10 for optical fiber feedthrough using axial seals for bi-directional sealing.
Invention is credited to James R. Dunphy, John J. Grunbeck, Roddie R. Smith, George J. Talmadge, Khai Tran.
Application Number | 20080166099 12/050655 |
Document ID | / |
Family ID | 40637409 |
Filed Date | 2008-07-10 |
United States Patent
Application |
20080166099 |
Kind Code |
A1 |
Dunphy; James R. ; et
al. |
July 10, 2008 |
OPTICAL FIBER FEEDTHROUGH USING AXIAL SEALS FOR BI-DIRECTIONAL
SEALING
Abstract
An optical waveguide feedthrough assembly passes at least one
optical waveguide through a bulk head, a sensor wall, or other
feedthrough member. The optical waveguide feedthrough assembly
comprises a cane-based optical waveguide that forms a glass plug
sealingly disposed in a feedthrough housing. A seal fills an
annular space between the glass plug and the housing. The seal may
be energized by a fluid pressure in the housing to establish
sealing engagement. Further, the seal may provide bidirectional
sealing. The feedthrough assembly is operable in high temperature
and high pressure environments.
Inventors: |
Dunphy; James R.; (South
Glastonbury, CT) ; Talmadge; George J.; (Clinton,
CT) ; Grunbeck; John J.; (Northford, CT) ;
Tran; Khai; (Pearland, TX) ; Smith; Roddie R.;
(Cypress, TX) |
Correspondence
Address: |
PATTERSON & SHERIDAN, L.L.P.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
40637409 |
Appl. No.: |
12/050655 |
Filed: |
March 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11172616 |
Jun 30, 2005 |
|
|
|
12050655 |
|
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Current U.S.
Class: |
385/138 ;
374/E11.015 |
Current CPC
Class: |
E21B 47/135 20200501;
G02B 6/02209 20130101; G02B 6/4248 20130101; G02B 6/4428 20130101;
G02B 6/022 20130101; G01L 11/025 20130101; G01K 11/32 20130101;
E21B 33/0385 20130101 |
Class at
Publication: |
385/138 |
International
Class: |
G02B 6/00 20060101
G02B006/00 |
Claims
1. An optical waveguide feedthrough assembly, comprising: a housing
having a bore extending therethrough; an optical waveguide element
having a core and cladding at a first section, wherein the first
section is disposed in the bore and has a larger cladding outer
diameter than a second section; a first sealing element disposed
around the first section of the optical waveguide element, wherein
the first sealing element has sealing lips oriented to be energized
into sealing engagement with the bore and the glass plug by fluid
pressure acting in a first direction within the bore; and a second
sealing element disposed around the first section of the optical
waveguide element, wherein the second sealing element has sealing
lips oriented to be energized into sealing engagement with the bore
and the glass plug by fluid pressure acting in a second direction
opposite the first direction within the bore.
2. The assembly of claim 1, wherein each of the first and second
sealing elements comprise a plurality of v-ring seals.
3. The assembly of claim 2, wherein the v-ring seals are made of a
thermoplastic.
4. The assembly of claim 2, wherein the v-ring seals are arranged
such that the v-ring seals made of a first material alternate with
the v-ring seals made of a second material different than the first
material.
5. The assembly of claim 4, wherein at common conditions the first
material is more rigid than the second material.
6. The assembly of claim 1, wherein the second section comprises an
optical fiber.
7. The assembly of claim 1, wherein the first and second sections
of the waveguide element are fused together.
8. The assembly of claim 1, wherein the sealing elements are
moveable relative to the optical waveguide element and the
housing.
9. The assembly of claim 1, wherein none of the waveguide element,
the sealing elements and the housing are bonded together.
10. The assembly of claim 1, wherein the optical waveguide element
has first and second convex frustoconical sections seated within
complimentary concave frustoconical sections along the bore.
11. The assembly of claim 1, further comprising a containment
member secured within the housing, wherein the containment member
has corresponding features mated with a profile of the cladding
outer diameter where the optical waveguide element has portions
with at least two different diameters.
12. An optical waveguide feedthrough assembly, comprising: a
housing having a bore extending therethrough; an optical waveguide
element having a core and cladding, wherein the optical waveguide
element is disposed in the bore and has a cladding outer diameter
with a profile defining sections with at least two different
diameters; a sealing element disposed around the first section of
the optical waveguide element and in sealing engagement with the
bore and the glass plug; and a containment member secured within
the housing, wherein the containment member has corresponding
features mated with the profile of the optical waveguide
element.
13. The assembly of claim 12, wherein the sealing element comprises
a plurality of v-ring seals.
14. The assembly of claim 12, wherein the sealing element comprises
a first plurality of v-ring seals oriented in an opposite direction
from a second plurality of v-ring seals.
15. The assembly of claim 12, wherein the containment member
defines a clam shell made of a thermoplastic.
16. The assembly of claim 12, wherein the containment member is
secured within the housing between inward facing shoulders of the
housing.
17. An optical waveguide feedthrough assembly, comprising: a
housing having a bore extending therethrough; an optical waveguide
element having a core and cladding at a first section with a larger
cladding outer diameter than a second section, wherein the first
section is disposed in the bore; and v-ring seals disposed around
the first section of the optical waveguide.
18. The assembly of claim 17, wherein a first plurality of the
v-ring seals are oriented in an opposite direction from a second
plurality of the v-ring seals.
19. The assembly of claim 18, further comprising an o-ring seal
disposed between the first plurality of the v-ring seals and the
second plurality of the v-ring seals.
20. The assembly of claim 17, further comprising a containment
member secured within the housing, wherein the containment member
has corresponding features mated with a profile of the cladding
outer diameter where the optical waveguide element has portions
with at least two different diameters.
21. The assembly of claim 17, wherein the v-ring seals are arranged
such that the v-ring seals made of polyetheretherketone alternate
with the v-ring seals made of polytetrafluoroethylene.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending
U.S. patent application Ser. No. 11/172,616, filed Jun. 30, 2005,
which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention relate to feedthroughs for
optical waveguides, and more particularly, to hermetically sealed
feedthroughs suitable for use in high pressure, high temperature,
and/or other harsh environments.
[0004] 2. Description of the Related Art
[0005] In many industries and applications, there exists a need to
have optical waveguides penetrate a wall, bulkhead, or other
feedthrough member wherein a relatively high fluid or gas
differential pressure exists across the feedthrough member. In
addition, one or both sides of the feedthrough member may be
subjected to relatively high temperatures and other harsh
environmental conditions, such as corrosive or volatile gas, fluids
and other materials. However, several problems exist that are
associated with constructing such an optical fiber feedthrough.
[0006] One of these problems relates to susceptibility of glass
fiber to damage and breakage due to flexibility based on a small
size of the fiber, brittle nature of glass material, and presence
of a significant stress concentration at the point where the fiber
enters and exits the feedthrough. Another problem with sealing an
optical fiber occurs due to fused silica material of which the
optical fiber is made having a low thermal expansion rate compared
to most engineering materials, including metals, sealing glasses
and epoxy. This difference in coefficients of thermal expansion
greatly increases the thermal stress problem at any
glass-to-sealing material interface. For example, epoxy used to
seal and fill around the fiber may due to thermal changes break its
bond with surrounding metal surfaces and/or the fiber, thereby
creating potential leak paths. Such thermal changes may occur in
use, during transport that may be in an aircraft, or even at
manufacturing where the epoxy may be molded at increased
temperatures prior to cooling.
[0007] One technique used to produce optical fiber feedthroughs is
the use of a sealed window with an input and an output lensing
system. In this technique, the optical fiber must be terminated on
each side of a pressure-sealed window, thus allowing the light to
pass from the fiber into a lens, through the window, into another
lens, and finally into the second fiber. The disadvantages
associated with this system include the non-continuous fiber path,
the need to provide two fiber terminations with mode matching
optics, thus increasing manufacturing complexity and increasing the
light attenuation associated with these features.
[0008] Therefore, a need exists for an improved optical waveguide
feedthrough assembly.
SUMMARY OF THE INVENTION
[0009] Embodiments of the invention provide an optical waveguide
feedthrough assembly, and a method of making such an assembly,
which is capable of relatively long-lasting operation at relatively
high pressures and/or temperatures. An optical waveguide
feedthrough assembly in one embodiment includes a housing having a
bore extending therethrough and an optical waveguide element having
a core and cladding at a first section, wherein the first section
is disposed in the bore and has a larger cladding outer diameter
than a second section. The feedthrough assembly further includes a
first sealing element disposed around the first section of the
optical waveguide element, wherein the first sealing element has
sealing lips oriented to be energized into sealing engagement with
the bore and the glass plug by fluid pressure acting in a first
direction within the bore. In addition, a second sealing element
may surround the first section of the optical waveguide element and
have sealing lips oriented to be energized into sealing engagement
with the bore and the glass plug by fluid pressure acting in a
second direction opposite the first direction within the bore.
[0010] An optical waveguide feedthrough assembly for one embodiment
includes a housing having a bore extending therethrough and an
optical waveguide element having a core and cladding, wherein the
optical waveguide element is disposed in the bore and has a
cladding outer diameter with a profile defining sections with at
least two different diameters. A sealing element disposed around
the first section of the optical waveguide element provides sealing
engagement with the bore and the glass plug. Further, a containment
member secured within the housing includes corresponding features
mated with the profile of the optical waveguide element.
[0011] In one embodiment, an optical waveguide feedthrough assembly
includes a housing having a bore extending therethrough. An optical
waveguide element includes a core and cladding at a first section
with a larger cladding outer diameter than a second section. The
feedthrough assembly further includes the first section disposed in
the bore and v-ring seals disposed around the first section of the
optical waveguide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings.
[0013] It is to be noted, however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0014] FIG. 1 illustrates a cross section view of an optical
waveguide feedthrough assembly.
[0015] FIG. 2 illustrates a cross section view of an optical
waveguide feedthrough assembly having diagnostic sensors disposed
therein.
[0016] FIGS. 3-5 illustrate graphs of signals received from the
diagnostic sensors where the feedthrough assembly is at a fixed
temperature and different pressure for each graph.
[0017] FIGS. 6-8 illustrate graphs of signals received from the
diagnostic sensors where the feedthrough assembly is at a fixed
pressure and different temperature for each graph.
[0018] FIG. 9 illustrates a cross section view of an optical
waveguide feedthrough assembly that provides bidirectional seal
performance.
[0019] FIG. 10 illustrates a cross sectional view of an optical
waveguide feedthrough assembly that includes a compression seal
element.
[0020] FIG. 11 illustrates the optical waveguide feedthrough
assembly shown in FIG. 10 after compression of the compression seal
element.
[0021] FIG. 12 illustrates a cross section view of another optical
waveguide feedthrough assembly.
[0022] FIG. 13 illustrates a cross section view of an optical
waveguide feedthrough assembly that provides bidirectional seal
performance utilizing first and second sets of multiple v-ring
seals with the sets oriented in opposing directions.
[0023] FIG. 14 illustrates a cross section view of an optical
waveguide feedthrough assembly including a plurality of v-ring
seals and a containment member to trap a glass plug within the
feedthrough assembly.
[0024] FIG. 15 illustrates a cross section view of an optical
waveguide feedthrough assembly that provides bi-directional seal
performance utilizing v-ring seals open towards an o-ring seal on
each side of the o-ring seal.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] Epoxy-free optical fiber feedthrough assemblies applicable
for use in high temperature, high pressure environments are
provided. In one embodiment, a feedthrough assembly includes a
glass plug disposed in a recess of a feedthrough housing. The glass
plug is preferably a large-diameter, cane-based, waveguide adapted
to seal the recess in the housing and provide optical communication
through the housing. All embodiments described herein provide for
sealing with respect to the housing at or around the glass plug of
an optical waveguide element passing through the housing.
[0026] As used herein, "optical fiber," "glass plug" and the more
general term "optical waveguide" refer to any of a number of
different devices that are currently known or later become known
for transmitting optical signals along a desired pathway. For
example, each of these terms can refer to single mode, multi-mode,
birefringent, polarization maintaining, polarizing, multi-core or
multi-cladding optical waveguides, or flat or planar waveguides.
The optical waveguides may be made of any glass, e.g., silica,
phosphate glass, or other glasses, or made of glass and plastic, or
solely plastic. For high temperature applications, optical
waveguides made of a glass material is desirable. Furthermore, any
of the optical waveguides can be partially or completely coated
with a gettering agent and/or a blocking agent (such as gold) to
provide a hydrogen barrier that protects the waveguide. In
addition, the feedthrough assemblies can include a single such
optical waveguide or may include a plurality of such optical
waveguides.
An Exemplary Feedthrough Assembly
[0027] FIG. 1 shows a cross section view of an optical fiber
feedthrough assembly 100 that includes a front housing 10 coupled
to a back housing 12. An optical waveguide element 14 passes
through a passageway 16 common to both housings 10, 12. The
passageway 16 is defined by bores extending across the housings 10,
12. The optical waveguide element 14 includes a glass plug 18
defining a large-diameter, cane-based, optical waveguide with an
outer diameter of about 0.3 millimeters (mm) or greater, such as
between 0.5 mm and 6.0 mm. The glass plug 18 can have appropriate
core and cladding dimensions and ratios to provide the desired
outer large-diameter.
[0028] For some embodiments, first and second fiber pigtails 19, 20
extend from each end of the glass plug 18. Each of the pigtails 19,
20 preferably include an optical waveguide such as an optical fiber
26 encased or embedded in a carrier 28 or larger diameter glass
structure allowing the fiber 26 to be optically coupled to the
glass plug 18. U.S. Patent Application Publication Number
2004/0165834, entitled "Low-Loss Large-Diameter Pigtail" and hereby
incorporated by reference in its entirety, describes exemplary
pigtails that can facilitate subsequent optical connection of the
fiber 26 to other fibers, connectors, or other optical components
by suitable splicing techniques known in the art. Further, U.S.
Application Publication Number 2004/0165841, entitled "Large
Diameter Optical Waveguide Splice," which is herein incorporated by
reference in its entirety, describes a large-diameter splice
suitable for splicing the fiber pigtails 19, 20 to the glass plug
18. For some embodiments, the glass plug 18 can be spliced to or
otherwise optically coupled with fibers in optical communication
with each end of the glass plug 18 by other techniques and
methods.
[0029] Sealing of the optical waveguide element 14 with respect to
the front housing 10 occurs at and/or around the glass plug 18 to
enable isolation of fluid pressure in communication with a first
end 22 of the passageway 16 from fluid pressure in communication
with a second end 24 of the passageway 16. This sealing of the
glass plug 18 with respect to the front housing 10 provides the
feedthrough capabilities of the feedthrough assembly 100. In the
embodiment shown in FIG. 1, the glass plug 18 has a cone shaped
tapered surface 50 for seating against a complimentary tapered seat
51 of the front housing 10. Engagement between the tapered surface
50 and the complimentary tapered seat 51 that is located along the
passageway 16 forms a seal that seals off fluid communication
through the passageway 16. The glass plug 18 can be machined to
provide the cone shaped tapered surface 50. Additionally, the glass
plug 18 is preferably biased against the tapered seat 51 using a
mechanical preload.
[0030] A recess 30 formed in one end of the front housing 10 aligns
with a corresponding recess 31 in one end of the back housing 12
where the housings 10, 12 are coupled together. Preferably, the
front housing 10 is welded to the back housing 12 along mated
features thereof. Materials for the housings 10, 12 depend on the
exact application. For example, Inconel 718 may make up the
housings 10, 12 for oil field service while more benign
applications may utilize a stainless steel. The housings 10, 12
preferably enclose the glass plug 18, a biasing member such as a
first stack of Belleville washers 34, and a plunger 32, which are
all disposed within the recesses 30, 31.
[0031] The first stack of Belleville washers 34 supply the
mechanical preload by pressing the plunger 32 onto an opposite end
of the glass plug 18 from the tapered surface 50. Since the plunger
32 is moveable with the glass plug 18, this pressing of the plunger
32 develops a force to bias the glass plug 18 onto the tapered seat
51 of the front housing 10 located along the passageway 16 that
passes through the front housing 10. Transfer of force from the
plunger 32 to the glass plug 18 can occur directly via an interface
54 between the two, which can include mating conical surfaces. The
first stack of Belleville washers 34 compress between a base
shoulder 44 of the recess 31 in the back housing 12 and an outward
shoulder 46 of the plunger 32 upon make-up of the front housing 10
to the back housing 12. Once the back housing 12 is welded or
otherwise attached to the front housing 10 in order to keep the
front and back housings 10, 12 connected, the first stack of
Belleville washers 34 maintains the compression that supplies force
acting against the plunger 32.
[0032] In some embodiments, the feed through assembly 100 further
includes a gasket member 52 disposed between the tapered seat 51
and the tapered surface 50 of the glass plug 18. As shown in FIG.
1, the gasket member 52 comprises an annular gasket. The gasket
member 52 may be a gold foil that is shaped to complement the
tapered surface 50 and the tapered seat 51. The gasket member 52
deforms sufficiently to accommodate imperfections on the tapered
surface 50 and/or the tapered seat 51, thereby completing the seal
and reducing stress between contacting surfaces due to any
imperfections on the surfaces. Gold is preferred because of its
ability to withstand high temperature, its ductility and its inert,
non-reactive, non-corrosive nature. However, other materials
possessing these characteristics may also be suitable, including
aluminum, lead, indium, polyetheretherketone ("PEEK.andgate."),
polyimide, other suitable polymers, and combinations thereof.
[0033] An additional gasket member (not shown) may be disposed
between the interface 54 of the glass plug 18 and the plunger 32
for some embodiments to reduce the surface stress that may occur
between these two components. In further embodiments, a layer of
gold or other suitable material is deposited on the contact
surfaces as an alternative to using the gasket member 52. For
example, the gold may be deposited using chemical vapor deposition,
physical vapor deposition, plating, or combinations thereof to
reduce surface stress and maximize the seal performance. Other
embodiments utilize the gasket member 52 punched from sheets of a
gasket material.
[0034] For some embodiments, the housings 10, 12 additionally
enclose a cup-shaped backstop sleeve 36, a second stack of
Belleville washers 38, a perforated washer 40, and a centering
element 42 that are all disposed within the recesses 30, 31. An
outward shoulder 56 of the backstop sleeve 36 is trapped by the end
of the front housing 10 and an inward shoulder 57 along the recess
31 in the back housing 12. Contact upon sandwiching of the shoulder
56 of the backstop sleeve 36 provides the point at which the
housings 10, 12 are fully mated and can be secured together.
Clearance is provided such that the end of the back housing 12 does
not bottom out prior to the housings 10, 12 being fully mated.
[0035] The centering element 42 includes an elastomeric sealing
component disposed between the glass plug 18 and the front housing
10 that can act as a back-up seal in addition to facilitating
alignment of the glass plug 18 with respect to the seat 51.
Although the centering element 42 is described as providing a back
up seal to the tapered surface 50 of the glass plug 18 seated with
the gasket member 52 on the complimentary tapered seat 51, the
centering element 42 can be omitted or used independently to seal
off the passageway 16 through the housings 10, 12 in other
embodiments.
[0036] In some applications, the pressure in the recesses 30, 31
entering from the second end 24 of the passageway 16 is higher than
the pressure entering from the first end 22 of the passageway 16.
This pressure differential advantageously causes the centering
element 42 to deform and press against the wall of the recess 30
and the wall of the glass plug 18, thereby creating a pressure
energized seal. In some embodiments, one or more holes or annular
channels 43 are formed on the outer surface of the high pressure
side of the centering element 42. These holes or channels 43
facilitate the deformation of the centering element 42 and the
formation of the seal between the centering element 42 and the
walls of the recess 30 and the glass plug 18. Additionally, the
perforated washer 40 enables pressurized fluid to fill the
centering element 42 for providing the energized seal.
[0037] Preferably, force transferred through the perforated washer
40 biases the centering element 42 into the recess 30. The second
stack of Belleville washers 38 pressed by the backstop sleeve 36
supplies the preloading force to the perforated washer 40. The
second stack of Belleville washers 38 allow a maximum pressure
force to act on the centering element 42 such that pressure of the
centering element 42 against the wall of the glass plug 18 does not
override force being put on the glass plug 18 to press the tapered
surface 50 against the seat 51.
[0038] Embodiments of the feedthrough assembly 100 are capable of
performing in temperature environments of between -50.degree. C.
and 300.degree. C. Additionally, differential pressures up to about
30 kpsi can be applied across the feedthrough seal and maintained
without leakage across the seal. The pressure rating of the housing
should be about the same as the seal, but depends on the exact
application.
Embedding Diagnostic Sensors
[0039] FIG. 2 illustrates a cross section view of an optical
waveguide feedthrough assembly 200 that operates similar to the
feedthrough assembly 100 shown in FIG. 1. However, the feedthrough
assembly 200 includes first and second diagnostic sensors 201, 202
disposed within a glass plug 218. The diagnostic sensors 201, 202
can include any optical sensing element, such as fiber Bragg
gratings, capable of reflecting or transmitting an optical signal
in response to a parameter being measured. The first diagnostic
sensor 201 is disposed within the glass plug 218 proximate an
interface 254 where a plunger 232 pushes on the glass plug 218. The
second diagnostic sensor 202 is disposed within the glass plug 218
proximate where a tapered surface 250 of the glass plug 218 mates
with a seat 251. Preferably, each of the diagnostic sensors 201,
202 span a length of the glass plug 218 across the respective
feature that the sensor is proximate.
[0040] Interpreting the signals generated by the sensors 201, 202,
such as by use of a suitable algorithm or comparison to a
calibration, enables monitoring of temperature and/or pressure.
This detection ability allows real-time monitoring of the state of
the feedthrough assembly 200. Information derived from the sensors
201, 202 can be beneficial both during fabrication of the
feedthrough assembly 200- and during use thereof. For diagnostic
purposes, signals received from the second sensor 202 can be
monitored to identify when and/or if proper contact of the tapered
surface 250 with the seat 251 occurs to ensure that sealing is
established or maintained. Further, monitoring one or both the
sensors 201, 202 can ensure that excess force that might break the
glass plug 218 is not applied to the glass plug 218 in embodiments
where the amount of force can be controlled. Monitoring signals
received from the first sensor 201 can detect the presence and
condition of hydrostatic loads from surrounding fluid since these
hydrostatic loads dominate the response of the first sensor 201.
When the feedthrough assembly 200 is part of a wellhead outlet of
an oil/gas well, the sensors 201, 202 can be used to detect
pressure increases and set an alarm indicating that seals have been
breached in the well.
[0041] FIGS. 3-5 illustrate graphs of signals received from the
diagnostic sensors 201, 202 where the feedthrough assembly 200 is
at a fixed temperature but has different pressures introduced at
end 224 for each graph. In all of the graphs herein, first sensor
responses 301 correspond to signals received from the first sensor
201 while second sensor responses 302 correspond to signals
received from the second sensor 202. In FIG. 3, an initial
distortion or spreading of the second sensor response 302 visible
specifically as a spectral chirp 303, providing positive feedback
that preload of the glass plug 218 at the tapered surface 250
against the seat 251 has been established.
[0042] As visible in FIGS. 4 and 5, this distortion in the second
sensor responses 302 grows relative to pressure due to non-uniform
seal loads. However, the first sensor responses 301 show little
change as pressure increases since uniform hydrostatic pressure
dominates the first sensor 201. Additionally, the first sensor
responses 301 provide an indication of a thermo-mechanical state of
the housing of the feedthrough assembly 200 and a small pressure
driven change in the preload of the plug 218.
[0043] FIGS. 6-8 show graphs of signals received from the
diagnostic sensors 201, 202 where the feedthrough assembly 200 is
at a fixed pressure but is at a different temperature for each
graph. The graphs show that as temperature increases both of the
responses 301, 302 shift in wavelength relative to the temperature
increase in the same direction. For example, the peak at
approximately 1534.5 nanometers (nm) in the first responses 301 at
25.degree. C. shifts to approximately 1536.5 nm at 194.degree. C.
Other than small changes from temperature driven changes in the
preloads, shapes of the responses 301, 302 do not change with
temperature changes.
[0044] With reference to FIG. 1, pressure entering the first end 22
of the passageway 16 may be significantly higher than the pressure
entering the second end 24 of the passageway 16 in some
applications. In this instance, if the higher pressure from the
first end 22 exceeds a threshold value, then the seals formed by
the seated tapered surface 50 of the glass plug 18 and/or the
centering element 42 may be unseated. Accordingly, non-epoxy
feedthrough assemblies in some embodiments can be adapted to seal
against pressure from either side of a glass plug.
A Bi-Directional Seal Assembly
[0045] FIG. 9 shows an exemplary feedthrough assembly 900 having a
bi-directional pressurized seal assembly 930. A glass plug 920
forms a waveguide as described herein. The glass plug 920 is cone
shaped and is disposed in a recess 925 of a feedthrough housing 910
formed by two body sections 911, 912. The body sections 911, 912
can be coupled together using a weld or various other coupling
configurations. A bore 915 sized to accommodate portions of an
optical waveguide element 922 on either side of the glass plug 920
extends through the feedthrough housing 910. A tapered seat 913 can
be formed on each body section 911, 912 for receiving the glass
plug 920. Similar to the embodiment shown in FIG. 1, a gasket
member 945 such as an annular gold foil can be disposed between the
glass plug 920 and the tapered seats 913 of the body sections 911,
912. The symmetrical configuration of tapered seats 913 in sections
911, 912 creates the primary bidirectional seal design.
[0046] In one embodiment, a back-up bi-directional seal assembly
930 is disposed in the recess 925 to provide an additional seal
against any leakage from either body section 911, 912. The seal
assembly 930 includes two cup-shaped, annular sealing elements 931,
932 and a positioning device 940 to maintain the sealing elements
931, 932 in their respective seal seats 941, 942. The sealing
elements 931, 932 are positioned such that their interior portions
are opposed to each other and the positioning device 940 may be
disposed in the interior portions of the sealing elements 931, 932.
The positioning device 940 may comprise a preloaded spring to bias
the sealing elements 931, 932 against their respective seal seats
941, 942, or against the body sections 911, 912. In one embodiment,
the sealing elements 931, 932 are made of an elastomeric material.
The sealing elements 931, 932 can also comprise other suitable
flexible materials capable of withstanding high temperature and
high pressure.
[0047] In operation, if fluid leaks through the tapered surfaces
between the glass plug 920 and the first body section 911, then the
fluid pressure forces the glass plug 920 against the tapered seat
in the body section 912 to activate the reverse direction seal. The
fluid pressure will also act against the second sealing element
932, which is biased against the second body section 912.
Particularly, the fluid pressure acts on the interior portion of
the second sealing element 932 and urges sealing lips 934 of the
second sealing element 932 outward, thereby sealing off any fluid
path between the second sealing element 932 and the glass plug 920
and between the second sealing element 932 and the body section
911. In this manner, the leaked fluid is prevented from entering
the bore of the second body section 912 because of redundant
seals.
[0048] Similarly, if fluid leaks through the tapered surfaces
between the glass plug 920 and the second body section 912, then
the fluid pressure forces the glass plug 920 against the tapered
seat 913 in body section 911. The fluid pressure will also act
against the first sealing element 931 biased against the first body
section 911. In this respect, the fluid pressure causes sealing
lips 933 of the first sealing element 931 to sealingly engage the
glass plug 920 and the body section 911. Thus, the leaked fluid is
prevented from entering the bore of the first body section 911
because of redundant seals.
Feedthrough Assembly with Compression Bushing
[0049] FIG. 10 illustrates a cross sectional view of an optical
waveguide feedthrough assembly 500 that includes a housing 110, an
externally threaded bushing 102, a compression driver bushing 104,
a compression seal element 106, and a glass plug 118 portion of an
optical waveguide element that sealingly passes through the housing
110. The bushings 102, 104 and the seal element 106 are disposed
adjacent to one another in a recess 130 in the housing 110 and
encircle a portion of the glass plug 118. Specifically, the
externally threaded bushing 102 threads into a portion of the
recess 130 in the housing 110 defining mating internal threads. The
seal element 106 is located next to the driver bushing 104 and
proximate an inward tapering cone 131 along the recess 130 in the
housing 110.
[0050] A seal can be established with the glass plug 118 with
respect to the housing 110 by driving the seal element 106 down the
cone 131. To establish this seal, rotation of the threaded bushing
102 with respect to the housing 110 displaces the threaded bushing
102 further into the recess 130 due to the threaded engagement
between the threaded bushing 102 and the housing 110. The driver
bushing 104 in turn moves further into the recess and pushes the
sealing element 106 toward the cone 131. One function of the driver
bushing 104 includes reducing torque transferred to the seal
element 106 from the threaded bushing 102.
[0051] Preferably, the glass plug 118 has a cone shaped tapered
surface 150 for seating against a complimentary tapered seat 151 of
the housing 110. The engagement between the tapered surface 150 and
the complimentary tapered seat 151 can also or alternatively seal
off fluid communication through the housing 110 around the glass
plug 118 in a redundant manner. A gasket member 152 such as an
annular gold foil can be disposed between the tapered surface 150
of the glass plug 118 and the tapered seat 151 of the housing 110
to reduce stress risers.
[0052] FIG. 11 illustrates the optical waveguide feedthrough
assembly 500 after compressing the seal element 106. The seal
element 106 packs within an annulus between an exterior of the
glass plug 118 and an interior of the housing 110 after being
driven down the cone 131. Once packed in the annulus, the seal
element 106 provides sealing contact against both the glass plug
118 and the housing 110. Examples of suitable materials for the
seal element 106 include TEFLON.TM., VESPEL.TM., polyimide,
PEEK.TM., ARLON.TM., gold or other ductile metals for high
temperature applications. During lower temperature usage, element
106 can be nylon, DELRIN.TM. or metal such as tin or lead. The
driving of the seal element 106 can additionally move the glass
plug 118 to force the tapered surface 150 to mate with the seat
151. The glass plug 118 is of sufficient diameter and structural
integrity that the compression of the seal element 106 around the
glass plug does not disturb the optical qualities thereof. The
feedthrough assembly 500 is capable of sealing the glass plug 118
with respect to the housing 110 regardless of which side of the
housing 110 is exposed to a higher pressure.
An Additional Exemplary Feedthrough Assembly
[0053] FIG. 12 shows a cross-section view of a feedthrough assembly
400 that includes a feedthrough housing 410 for retaining a glass
plug 418. A recess 425 is formed in one end of the housing 410 to
receive the glass plug 418. Preferably, the recess 425 has a
corresponding tapered seat 451 for receiving a cone shaped tapered
surface 450 of the glass plug 418. The glass plug 418 is preferably
biased against the tapered seat 451 that is located along a bore
416 that connects to the recess 425 and provides a passageway
through the housing 410.
[0054] In one embodiment, a fitting 436 having an axial bore 437
extending therethrough is disposed between the glass plug 418 and a
washer cap 412. One end of the fitting 436 has a surface that mates
with the glass plug 418 and an outer diameter that is about the
same size as the inner diameter of the recess 425. In this respect,
the fitting 436 assists with supporting the glass plug 418 in the
recess 425. The other end of the fitting 436 has a neck 435 that
connects to the washer cap 412. Particularly, a portion of the neck
435 fits in a hole of the washer cap 412. The washer cap 412 may be
attached to the feedthrough housing 410 by any manner known to a
person of ordinary skill in the art, such as one or more screws or
bolts. For example, bolts 438 (two of three are visible in FIG. 12)
may be used to attach the washer cap 412 to the feedthrough housing
410 via three screw holes 440 (only one is visible in FIG. 12)
formed through the washer cap 412 and into the feedthrough housing
410.
[0055] The inner portion of the washer cap 412 facing the
feedthrough housing 410 has a cavity 431 for retaining a preload
member such as a spring. In one example, the preload member is a
Belleville washer stack 434. The washer stack 434 may be disposed
on the neck 435 of the fitting 436 and between the washer cap 412
and an outward shoulder 446 formed by a reduced diameter of the
neck 435 of the fitting 436. In this manner, the washer stack 434
may exert a preloading force on the glass plug 418 to maintain a
seal between the glass plug 418 and the tapered seat 451 of the
feedthrough housing 410. Similar to the embodiments described
above, a gasket member such as an annular gold foil (not shown) can
be disposed between the glass plug 418 and the tapered seats 451
and/or the glass plug 418 and the fitting 436.
[0056] The feedthrough assembly 400 may further include a centering
element 442 to act as a back-up seal. The centering element 442
comprises an elastomeric sealing component that is disposed between
the glass plug 418 and the feedthrough housing 410. A pressure
differential across the glass plug 418 advantageously causes the
centering element 442 to deform and press against the wall of the
recess 425 and the wall of the glass plug 418, thereby creating a
pressure energized seal. Although the centering element 442 is
described as providing a back up seal, the centering element 442
may be used independently to seal off the bore 416 of the
feedthrough housing 410.
Additional Bi-Directional Seal Assemblies
[0057] FIG. 13 illustrates an optical waveguide feedthrough
assembly 600 interfaced with tubing 601 and that provides
bi-directional seal performance similar to the assembly 900 shown
in FIG. 9. The feedthrough assembly 600 includes a glass plug 620
disposed in a recess 625 of a feedthrough housing 610 formed by
first and second body sections 611, 612 coupled together using a
weld for example. A bore 615 sized to accommodate portions of an
optical waveguide element 622 on either side of the glass plug 620
extends through the feedthrough housing 610. As with other
embodiments described herein, the glass plug 620 includes a core
and a cladding and may be fused to a section (e.g., a length of
optical fiber) of the waveguide element 622 with a relatively
smaller cladding outer diameter such that material forming the
glass plug 620 and the section of the waveguide element 622 with
the smaller outer diameter is continuous and adjoined without any
break. Further, the glass plug 620 may be retained within the
recess 625 by a tapered mating 613 between the glass plug 620 and
each of the body sections 611, 612 of the housing 610. The glass
plug 620 may lack any affixing to the housing 610 or preloading
against the housing 610 such that the glass plug 620 is freely
moveable within where retained. For some embodiments, the tapered
mating 613 may not form a seal but rather only prevent ejection
through the bore 615 of the glass plug 620 from the recess 625 due
to any pressure differential across the feedthrough assembly
600.
[0058] The feedthrough assembly 600 also includes first and second
sets 630, 631 of multiple chevron or v-ring seals 632 with the sets
630, 631 oriented in opposing directions from one another. The sets
630, 631 surround the glass plug 620 within the recess 625 and
provide sealing at distal lips of the v-ring seals 632 with an
outside surface of the glass plug 620 and an inside surface of the
housing 610 along the recess 625. The v-ring seals 632 of the first
set 630 open toward and receive force from fluid pressure entering
the feedthrough assembly 600 through the first body section 611
while the second set 631 open toward and receive force from fluid
pressure entering the feedthrough assembly 600 through the second
body section 612. The fluid pressure acts to urge the lips of the
v-ring seals 632 into sealing engagement with respective surfaces,
thereby sealing pressures from both sides of the feedthrough
assembly 600.
[0059] A spacer 633 separates the first and second sets 630, 631 in
embodiments where the v-ring seals 632 do not occupy all of the
length of the glass plug 620 within the recess 625 of the housing
610. In addition, each of the sets 630, 631 may include a male end
ring 634 and a female end ring 635 to aid in holding and
stabilizing the v-ring seals 632 disposed between the end rings
634, 635. The end rings 634, 635 fill voids or adapt any
surrounding surface shapes to that of the v-ring seals 632.
[0060] Exemplary materials for the multiple v-ring seals 632 within
each of the sets 630, 631 include fluoroelastomers, silicones,
thermoplastics, polyetheretherketone, polyimide and
polytetrafluoroethylene. Further, materials such as
polyetheretherketone and polytetrafluoroethylene may include
fillers, such as glass, carbon (graphite), or molybdenum fillers.
Selection of the material for the v-ring seals 632 depends on
pressures and temperatures anticipated for a working range of the
feedthrough assembly 600. The material may vary from one of the
v-ring seals 632 to another in order to achieve the working range
desired as discussed further with respect to FIG. 15. For example,
a first thermoplastic that is more rigid than a second
thermoplastic enables sealing at higher temperatures/pressures than
the second thermoplastic that is relatively softer and more
compliant and better suited for lower temperatures/pressures. By
having a plurality of the v-ring seals 632 within each of the sets
630, 631, redundant sealing occurs. The same material as the v-ring
seals 632 or a different material such as metal may form the end
rings 634, 635.
[0061] The v-ring seals 632 lack any bonding to the glass plug 620
or the housing 610 such that the v-ring seals 632 are movable
relative to the glass plug 620 and the housing 610, thereby
relieving stress at sealing interfaces. Such relative movement may
occur during heating or cooling of the feedthrough assembly 600 as
a result of differences in thermal expansion rates and does not
inhibit sealing capabilities of the v-ring seals 632. The v-ring
seals 632 function without reliance on a bonded interface that may
be broken with such stress at the sealing interfaces.
[0062] FIG. 14 shows an optical waveguide feedthrough assembly 700
including first and second v-ring sealing sets 730, 731. Without
repeating operational details, sealing of a glass plug 720 within
first and second body sections 711, 712 thus may occur as described
herein. The feedthrough assembly 700 further includes a containment
member 713 to trap the glass plug 720 within the feedthrough
assembly 700. In some embodiments, the containment member 713
defines a clam shell configuration to enable its placement around
the glass plug 720. At least one notch 714 machined into an outer
surface of the glass plug 720 mates with a corresponding dog 715 of
the containment member 713. The dog 715 forms a projection along an
inside diameter of the containment member 713.
[0063] Mating interlocked profiles or features such as the notch
714 and the dog 715 may vary in geometry, size and quantity while
still engaging one another to retain the glass plug 720 relative to
the containment member 713. The containment member 713 enables
multiple loading locations and distribution of the loading
locations along a length of the glass plug 720 so that forces
applied to the glass plug 720 by any pressure differentials across
the feedthrough assembly 700 are not concentrated at any one point.
This distribution of stress may benefit service life of the
feedthrough assembly 700 by inhibiting initiation and acceleration
of crack growth within the glass plug 720. The containment member
713 may further aid in alleviating stress on the glass plug 720 by
being made of a material (e.g., polyetheretherketone) that provides
a softer landing relative to the body sections 711, 712 of the
feedthrough assembly 700, for example.
[0064] The body sections 711, 712 of the feedthrough assembly 700
trap the containment member 713 via first and second inward facing
shoulders 716, 718. For example, first and second intermediary
spacers 717, 719 may receive an outside of the containment member
713 at respective ends thereof and also include portions with an
outer dimension greater than the inward facing shoulders 716, 718
between which the portions of the spacers 717, 719 are disposed.
The first intermediary spacer 717 extends toward the first v-ring
sealing set 730 and includes a female end face to support the first
v-ring sealing set 730. Likewise, the second intermediary spacer
719 extends toward the second v-ring sealing set 731 and includes a
female end face to support the second v-ring sealing set 731.
[0065] FIG. 15 illustrates an optical waveguide feedthrough
assembly 800 depicting an exemplarily configuration of a seal stack
830. Analogous to the feedthrough assembly 600 shown in FIG. 6, the
seal stack 830 engages and seals a glass plug 820 within body
sections 811, 812 of the feedthrough assembly 800. The seal stack
830 includes an optional o-ring 856 that is made of, for example, a
fluoroelastomer and enables lowest temperature/pressure sealing
within the seal stack 830. In a mirror image arrangement starting
from closest to the o-ring 856, the seal stack 830 additionally
includes male ring adapters 834, alternating first and second
v-rings 832, 833 and female ring adapters 835. The first v-ring
seals 832 provide sealing at a highest temperature/pressure using
the seal stack 830 and may be made of polyetheretherketone. The
second v-ring seals 833 provide sealing at an intermediate
temperature/pressure using the seal stack 830 and may be made of
polytetrafluoroethylene. At the intermediate temperature/pressure,
the first v-ring seals 832 limit creep/extrusion of the second
v-ring seals 833. The adapters 834, 835 that may be made of metal
thus limit creep/extrusion of the first v-ring seals 832 at the
highest temperature/pressure sealed using the seal stack 830.
[0066] The invention heretofore can be used and has specific
utility in applications within the oil and gas industry. Further,
it is within the scope of the invention that other commercial
embodiments/uses exist with one such universal sealing arrangement
shown in the figures and adaptable for use in (by way of example
and not limitation) industrial, chemical, energy, nuclear,
structural, etc. While the foregoing is directed to preferred
embodiments of the invention, other and further embodiments of the
invention may be devised without departing from the basic scope
thereof, and the scope thereof is determined by the claims that
follow.
* * * * *